Oyster setting method and apparatus

ABSTRACT

Oyster shells are fed in bulk from a storage hopper and allowed to free-fall into a setting tank containing liquid and freeswimming oyster larvae. The shells land on their convex side on a moving open-mesh conveyer. The conveyer transports the shells through the liquid and out of the tank. As the shells are passed through the liquid the larvae set on the convex undersides. As the shells leave the setting tanks with the larvae attached they are utilized in open-mesh bags and then placed in a recovery tank for a few days until suitably conditioned for transporting and placing in natural oyster beds.

United States Patent McMilIin [4 1 Oct. 31, 1972 s41 OYSTER SETTINGMETHOD AND 2,853,049 9/1958 Glancy ..119/4 APPARATUS 3,572,292 3/1971Quayle et al ..l l9/4 [72] inventor: David C. McMillin, Shelton, Wash.Primary Examiner Aldrich F. Medbery [73] Assignee: Olympia OysterCompany, Shelton, Atmmey Seed, Berry & Dowrey Wash.

1221 Filed: Dec. 10, 1970 [571 ABSTRACT 21 A L N 96 905 Oyster shellsare fed in bulk from a storage hopper 1 pp 0 and allowed to free-fallinto a setting tank containing liquid and free-swimming oyster larvae.The shells [52] US. Cl ..119/4 land on their convex side on a movingopen mesh [51] [1.1L Cl. ..A0lk 61/00 veyer The conveyer transports theShells through the [58] Field (It Search ..119/4 liquid and out of thetank. AS the shells are passed through the liquid the larvae set on theconvex under- [56] References cued sides. As the shells leave thesetting tanks with the lar- UNITED STATES PATENTS vae attached they areutilized in open-mesh bags and then placed in a recovery tank for a fewdays until 3,017,857 1/1962 Munz ..119/4 suitably di i d f transportingand placing in 3,526,209 9/1970 Budge ..119/4 natural Oyster beds.3,196,833 7/1965 Glancy ..119/4 1,933,950 11/1933 Wells ..119/4 7Claims, 2 Drawing Figures UNITlZlNG RECOVERING PAIENTEMBI 1 1912 3.701.338

FIG 11 UNITIZING SETTING RECOVERING INVENTOR. DAVID G. M6 MILLINATTORNEYS BACKGROUND OF THE INVENTION 1 Field of the Invention Thisinvention relates to the commercial production of seed oysters.

2. Description of the Prior Art For a period of time oyster larvae arefree-swimming and attach themselves or set on cultching material such asrocks, sticks, and especially previously harvested oyster shells. Oystershells are the primary source of cultching material because of theirgood quality, affinity to the larvae, and abundance in the oystergrowing regions.

The prior art cultching technique, that is, getting the larvae to set onoyster shells, was to unitize the shells either by stringing them on awire or bundling them in an openmesh sack. Unitizing is defined ascollecting or gathering the shells in a transportable container. Thestring or sack is then immersed in the water and exposed to. theswimming larvae. In using this technique, the distribution of larvae oneach shell was nut uniform causing overcrowding, and precluded properaccess to the available food in the water. The problem was particularlysevere when a high concentration of larvae were in the water as is thecase when cultching is done in tanks with laboratory or otherartificially produced larvae.

SUMMARY OF THE INVENTION Applicant has discovered, contrary to theheretofore customary practice of unitizing the oyster shells prior toexposure to the swimming larvae, that a better set, e. g., a betterdistribution of larvae among a large quantity of shells and a betterdistribution of larvae on each shell is obtainable by unitizing afterthe larvae have set. It is thus an object, of this invention, to providea commercial method and apparatus for obtaining a high quantity highquality set of oyster larvae on oyster shells.

It is the object of this invention, to obtain a set of oyster larvae onoyster shells at a low-cost.

It is an object of this invention, to obtain a consistent set of oysterlarvae on oyster shells and to obtain the set on the convex side of theshells.

Basically the method of this invention comprises feeding the oystershells in bulk into a liquid containing a high concentration offree-swimming oyster larvae. In the preferred form, the shells arepermitted to free-fall through the liquid a distance sufficient toenable them to come to rest with the convex side of the shell down. Nextthe shells are moved through the liquid and exposed to the free-swimminglarvae for a sufficient length of time to obtain a desired set. Once theset has occurred the oyster seed is unitized and stored or vice versa ina recovery liquid before being placed on their natural fattening beds.

The preferred apparatus employs an inclined conveyer movable through atank of liquid containing the free-swimming larvae. The shells arepermitted to freefall into the tank to the lower end of the conveyerwhich is spaced sufficiently below the surface of the liquid to enablethe shells to come to rest on the conveyer with their convex sides down.The conveyer is moved slowly through the liquid to obtain a proper setand the oyster seed is then unitized preferably at the end of theconveyor prior to being placed in a recovery liquid in a separate tank.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a preferred form ofapparatus suitable for carrying out the method of the invention.

FIG. 2 is an enlarged section taken along the line 2- 2 of FIG. 1illustrating the desired position of the shells on the conveyor and thegeneral location of the oyster larvae attached to the shell.

DESCRIPTION OF THE PREFERRED METHOD OF APPARATUS The apparatus suitablefor carrying out the method includes a hopper 10 having a discharge gate12 for controlling the flow of bulk oyster shells discharged therefrom.The hopper is positioned over the end of a setting tank 14. The tankcontains a setting liquid 16 preferably having a high concentration offreeswimming oyster larvae. The oyster larvae may be produced at thesite of the cultching operation or may be produced at a remote locationand shipped to the cultching location. The liquid can be controlled intemperature, salinity concentration, purity, etc., preferably, however,salt water at the location of the oyster growing region is directlypumped into the tank 14 and used as the setting liquid with generallyonly the temperature control necessary to obtain the optimum settingtime. Preferably the water temperature in the setting tank is between72-80F with the preferred exposure time of each shell in the liquidfalling within the range of 5 15 minutes.

Oyster survival is best when the set is on the convex side of theshells. In order to obtain this set consistently, characteristics of theshells and larvae are uniquely combined. First, free-swimming oysterlarvae generally set only on the underside of the shells. Second, oystershells because of their concave-convex shape will normally assume aconvex-side down position when free-falling in water. In this inventionthe shells are permitted to free-fall through the liquid to the lowerend of the open-mesh conveyer 18 a sufficient distance to allow theshells to land convex-side down on the conveyer. Thus by positioning allof the shells in a convex-down position it is possible to obtain most ofthe set on the desired convex-side.

The conveyer 18 is preferably open-mesh to allow the free-swimminglarvae access to the entire convexside of the shell. The conveyer isentrained around rollers 20 and powered in a conventional manner tocarry the shells out of the tank 14 where they are unitized by gatheringthem in open-mesh sacks 22. The unitized oyster seeds are then placed ina recovering tank 24. The recovering tank includes a liquid eitherpumped directly from the region in the oyster growing area orartificially controlled as in the same manner as the setting liquid 16.Preferably the water in the recovering tank is kept at a temperaturewithin the range -7 2F with the shells being held in the tank forbetween 4-5 days.

Finally the unitized oyster seed is removed from the recovering tank byconventional techniques and redeposited on the fattening beds in theirnatural habitat.

FIG. 2 demonstrates a typical shell S having a convex-underside 15 withlarvae L attached thereon. Obviously the exact location and number oflarvae setting on a particular shell varies; however, by maintaining thetemperature of the setting water (and thus the activity level of thelarvae) and maintaining the time in the tank, an average number can berealized. Since the entire convex underside 15 is exposed to thefreeswimming larvae a distribution over a greater area of the individualshell is achieved. As a result the larvae have more room to grow andmore access to their food source in the water.

The method of the invention is broadly to feed ununitized oyster shellsinto a liquid containing freeswimming oyster larvae. After exposure forsufficient time to obtain a desired set the seed oysters are unitizedand stored in a recovering liquid. In the alternative, unitizing cantake place after the recovering period using apparatus similar to thatused in the setting operation. In a preferred form of the method theshells are given sufficient free-falling distance through the liquid tocome to rest with their convexsides down.

While the preferred form of method and apparatus have been illustratedand described, it should be understood that modifications and additionswill be apparant to one skill in the art without departing fromprinciples of the invention. It is to be understood, therefore, that theinvention is not to be limited by the specific method and apparatusdescribed but only by the proper interpretation of the claims appendedhereto.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. The method of setting oyster larvae on shells or other cup-likecultching material comprising:

dispensing a flow of individual shells from a supply source,

providing a tank containing a liquid and freeswimming oyster larvae anda conveyor passing through said liquid,

permitting the dispensed shells to fall freely and be immersed in theliquid onto said conveyor,

holding the immersed shells in the liquid for a time sufficient toobtain a set of larvae on the shells, transferring the shells with theirset to a recovery area, holding the shells with their set in therecovery area for a time sufficient to reach young maturity, removingthe shells with their set from the recovery area and depositing them intheir natural habitat, and gathering the shells with their set in easilytransportable quantities into containers for ease of transportationprior to depositing them in their natural habitat.

2. The method of claim 1, said gathering step occuring prior to the stepof transferring the shells and set to the recovery area.

3. The method of claim 1, the step of permitting the shells to fallfreely includes allowing the shells to freefall through the liquid for adistance sufficient to permit the shells to reach convex-side-downpositions.

4. The method of claim 1, said liquid temperature in the tank is between72- F., said holding time to obl' h rir thci SFiiiiii's, said gatheringstep occurring prior to the step of transferring the shells and set tothe recovery area.

6. Apparatus for commercially setting large quantities of oyster larvaeon oyster shells comprising bulk storage means for holding a supply ofshells, gate means for dispensing a plurality of individual oystershells from said storage means into a setting tank, a setting liquidcontaining free-swimming oyster larvae in said tank, means in said tankfor moving the shells through the liquid, said means for moving theshells through the liquid including an open-mesh conveyor spaced belowthe top surface of the setting liquid a distance sufficient to allowsubstantially all the shells to free-fall through the liquid intoconvex-side-down positions on the conveyor, and means for collecting theshells in containers of easily transportable size after the larvae haveset thereon, and recovering means in proximity to the setting tank fortemporarily storing the collected shells.

7. The apparatus of claim 6 wherein the conveyor is on an angle and hasan upper discharge end and wherein the means for collecting the shellsis at the upper discharge end of the conveyor.

1. The method of setting oyster larvae on shells or other cuplikecultching material comprising: dispensing a flow of individual shellsfrom a supply source, providing a tank containing a liquid andfree-swimming oyster larvae and a conveyor passing through said liquid,permitting the dispensed shells to fall freely and be immersed in theliquid onto said conveyor, holding the immersed shells in the liquid fora time sufficient to obtain a set of larvae on the shells, transferringthe shells with their set to a recovery area, holding the shells withtheir set in the recovery area for a time sufficient to reach youngmaturity, removing the shells with their set from the recovery area anddepositing them in their natural habitat, and gathering the shells withtheir set in easily transportable quantities into containers for ease oftransportation prior to depositing them in their natural habitat.
 2. Themethod of claim 1, said gathering step occuring prior to the step oftransferring the shells and set to the recovery area.
 3. The method ofclaim 1, the step of permitting the shells to fall freely includesallowing the shells to free-fall through the liquid for a distancesufficient to permit the shells to reach convex-side-down positions. 4.The method of claim 1, said liquid temperature in the tank is between 7280* F., said holding time to obtain a set is 5 - 15 minutes.
 5. Themethod of claim 3, said gathering step occurring prior to the step oftransferring the shells and set to the recovery area.
 6. Apparatus forcommercially setting large quantities of oyster larvae on oyster shellscomprising bulk storage means for holding a supply of shells, gate meansfor dispensing a plurality of individual oyster shells from said storagemeans into a setting tank, a setting liquid containing free-swimmingoyster larvae in said tank, means in said tank for moving the shellsthrough the liquid, said means for moving the shells through the liquidincluding an open-mesh conveyor spaced below the top surface of thesetting liquid a distance sufficient to allow substantially all theshells to free-fall through the liquid into convex-side-down positionson the conveyor, and means for collecting the shells in containers ofeasily transportable size after the larvae have set thereon, andrecovering means in proximity to the setting tank for temporarilystoring the collected shells.
 7. The apparatus of claim 6 wherein theconveyor is on an angle and has an upper discharge end and wherein themeans for collecting the shells is at the upper discharge end of theconveyor.